1. Field of the Invention
The present invention relates to moving image encoding device/method for encoding a plurality of moving images in such a manner that the quality of moving images reproduced by a decoding device is enhanced after the process of compressing/encoding the plurality of moving images and multiplexing the encoded signals to generate moving image encoded signals at a constant bit rate.
The present invention also relates to moving image multiplexing device/method for multiplexing moving image encoded signals obtained after the process of compressing/encoding a plurality of moving images or moving image segments obtained by dividing a high-precision moving image.
The present invention further relates to an image transmission device which compresses/encodes a plurality of moving images and transmits the resultant moving image encoded signals at a limited bit rate, used in the moving image transmission for satellite communications or network communications such as a LAN, for example.
2. Description of the Related Art
In one of the methods for compressing/encoding and multiplexing a plurality of moving images to transmit the resultant moving images as a bit stream at a constant bit rate, a predetermined fixed bit rate is allocated for each of the moving images so that the sum of the bit amounts representing the plurality of moving images after the compression/encoding constitutes a constant bit rate. In such a method, when moving images with high complexity are input, the allocated bit rate is insufficient, resulting in great degradation in the image quality. Conversely, when moving images with low complexity are input, stuffing increases, resulting in wasteful use of the bit rate. As a result, two opposite problems arise. That is, when an effective use of the bit rate is attempted, the image quality lowers. Conversely, when high image quality is attempted, the bit rate is not effectively used, decreasing the number of moving images which can be multiplexed.
In order to solve the above problems, Japanese Laid-Open Publication No. 8-23540 discloses an encoding control device in which the bit rate at the encoding of respective moving image signals is made variable to improve the quality of moving images reproduced by a decoding device. In this encoding control device, the moving images reproduced from moving image encoded signals are compared with the original moving images. The bit rate is increased when a reproduced moving image is largely distorted from the original one, while it is decreased when a reproduced moving image is little distorted, so that the quality of the moving images is made uniform and thus the entire image quality improves.
According to the above method, however, the bit rate is changed after the amount of distortion is determined. Therefore, in the case where the moving images become complicated suddenly due to a scene change and the like, the quality of the moving image immediately after the scene change is low.
Moreover, in this conventional device in which the bit rate at the encoding of the moving images is variable, when a simple multiplexing operation is conducted such as changing the bit rate in proportion to the bit amount generated during a predetermined time period, an input buffer of a decoding device may cause overflow or underflow.
An encoding device which encodes moving images with different resolutions is disclosed in Japanese Laid-Open Publication No. 6-6777, for example. FIG. 37 shows the configuration of such an encoding device, where high-quality HDTV moving images are divided into a plurality of blocks by a frame synthesization blocking section 1101, and the resultant blocks are sent to a block distribution section 1102. When a signal switch 1107 which operates in response to an operation mode signal is switched to one terminal connecting with the block distribution section 1102, the block distribution section 1102 distributes the respective blocks received from the frame synthesization blocking section 1101 to moving image encoding sections 1103 to 1106. The moving image encoding sections 1103 to 1106 encode the respective blocks and output resultant encoded signals. When the signal switch 1107 is switched to the other terminal, TV moving images with a normal quality are supplied to the moving image encoding section 1103 via the signal switch 1107. The moving image encoding section 1103 encodes the TV moving images and outputs resultant encoded signals.
Thus, in this conventional device, both low-resolution moving image signals and high-resolution moving image signals can be encoded by switching the signal switch 1107.
However, the conventional device with the above configuration provides no conception of encoding and multiplexing moving images with different resolutions simultaneously. This device is therefore not applicable to the simultaneous transmission of moving images with different resolutions which is employed in broadcasting and the like.
In one conventional technique of multiplexing a plurality of moving images for transmission, a fixed bit rate is allocated for each encoding device, so that moving images are encoded by each encoding device at the allocated bit rate and resultant moving image encoded signals are multiplexed. However, this technique has the following problem. The complexity of moving images changes with time. Accordingly, in order to encode and transmit the moving images so that the degradation in the image quality is always inconspicuous, the respective bit rates are required to be set so that the degradation in the image quality of the reproduced moving image is inconspicuous even when a moving image with highest complexity is encoded. This lowers the transmission efficiency.
In order to solve the above problem, a method in which the bit rate is changed depending on the complexity of the encoding of moving images has been attempted. According to this method, the bit rate is lowered for simple moving images to realize efficient transmission, and multi-channel communication using more channels is possible f or the same transmission bit rate. This method is described in WO 95/32565, for example.
FIG. 38 shows a device implementing the above method. Referring to FIG. 38, moving image encoding sections 2101, 2102, and 2103 encode input moving images in accordance with respective target rates specified by a multiplexing section 2104, and output resultant encoded signals to the multiplexing section 2104. The multiplexing section 2104 multiplexes the received encoded signals and outputs multiplexed signals to a transmission route. The multiplexing section 2104 also adjusts the target rates based on a transmission rate for the encoded signals and supplies the new target rates to the moving image encoding sections 2101 to 2103.
The target rates are set so that a total of the target rates is equal to the transmission rate. More specifically, each of the moving image encoding sections 2101 to 2103 sends the amount of encoding distortion at the encoding to the multiplexing section 2104 every fixed period. The multiplexing section 2104 adjusts the target rate depending on the amount of encoding distortion sent from each of the moving image encoding sections 2101 to 2103 while the total of the target rates is kept equal to the transmission rate. That is, the target rate is increased for the moving image encoding section which has sent a large distortion amount, while it is lowered for the moving image encoding section which has sent a small distortion amount. In this way, moving images encoded by the moving image encoding sections 2101 to 2103 are provided with bit rates allocated depending on the complexity of the encoding.
In the above conventional method, however, the target rates are corrected so as to reduce the amount of distortion after the distortion is generated. Accordingly, the image quality tends to be low at an instance immediately after the scene change to a scene of which encoding is difficult, for example. Moreover, in this conventional method, the multiplexing section calculates the target rates to be allocated to the moving image encoding sections based on the amounts of encoding distortion in the moving image encoding sections. Therefore, when the number of moving image encoding sections connected to the multiplexing section is large, the amount of calculation required to allocate the target rates increases. Furthermore, if the moving image encoding sections are dispersed on a network and moving images are transmitted on the network, processings of collecting information on the encoding distortion from the respective moving image encoding sections and allocating the target rates to the respective moving image encoding sections are required. It is difficult to achieve these processings real time.
The moving image encoding device for encoding a plurality of moving image signals of this invention includes: a plurality of encoding sections for encoding the plurality of moving image signals, the encoding sections being provided with a plurality of quantization sub-sections for quantizing the plurality of moving image signals with predetermined quantization widths; and a quantization control section for controlling the quantization widths used by the quantization sub-sections simultaneously.
With the above configuration, the quality of the output moving images can be made uniform.
In one embodiment of the invention, the quantization widths used by the quantization sub-sections are the same.
In another embodiment of the invention, the moving image encoding device further includes a plurality of accumulation sections for temporarily accumulating a plurality of moving image encoded signals output from the plurality of encoding sections, wherein the quantization control section determines the quantization widths used by the quantization sub-sections based on a sum of bit amounts of the plurality of moving image encoded signals accumulated in the accumulation sections.
In still another embodiment of the invention, the moving image encoding device further includes a screen division section disposed upstream of the plurality of encoding sections for dividing an input moving image signal into a plurality of moving image signals.
According to another aspect of the invention, a moving image multiplexing device for multiplexing a plurality of moving image encoded signals obtained by encoding a plurality of moving image signals is provided. The device includes: a plurality of accumulation sections for temporarily accumulating the plurality of moving image encoded signals; a multiplexing section for multiplexing the plurality of moving image encoded signals accumulated in the plurality of accumulation sections and outputting the multiplexed signals at a constant bit rate; a decoding delay time calculation section for calculating a time period from when a specific bit of each of the plurality of moving image encoded signals is input into a decoding device until when the specific bit is decoded by the decoding device; a frame bit amount calculation section for calculating a bit amount of a frame including the specific bit of each of the plurality of moving image encoded signals accumulated in the plurality of accumulation sections; and a multiplexing control section for controlling a plurality of first input bit amount which are the bit amounts of the plurality of moving image encoded signals input from the plurality of accumulation sections to the multiplexing section based on calculation results of the decoding delay time calculation section and the frame bit amount calculation section.
With the above configuration, the multiplexing is conducted in constant consideration of the decoding delay time in the decoding device. Accordingly, the occurrence of overflow or underflow can be prevented at the decoding of the moving image encoded signals by the decoding device.
In one embodiment, the multiplexing control section includes: a first parameter generation sub-section for determining a plurality of first parameters each of which is a ratio of the bit amount calculated by the frame bit amount calculation section to the time calculated by the decoding delay time calculation section; a second parameter generation sub-section for determining a second parameter which is a sum of the plurality of first parameters; a third parameter generation sub-section for determining a plurality of third parameters each of which is a ratio of each of the plurality of first parameters to the second parameter for the plurality of moving image encoded signals accumulated in the plurality of accumulation sections; and a multiplex bit amount calculation section for calculating the plurality of first input bit amounts based on the plurality of third parameters.
In one embodiment of the invention, the moving image multiplexing device further includes: an accumulated bit amount calculation section for calculating the bit amounts of the plurality of moving image encoded signals accumulated in the plurality of accumulation sections; and an empty capacity calculation section for calculating an empty capacity of an input buffer of a decoding device immediately before a specific bit of each of the plurality of moving image encoded signals is input into the decoding device, wherein the multiplex bit amount calculation section sets for each of a plurality of second input bit amounts a minimum value among (1) the first input bit amount determined based on the third parameter, (2) the bit amount of the moving image encoded signal calculated by the accumulated bit amount calculation section, and (3) the empty capacity of the input buffer of the decoding device calculated by the empty capacity calculation section, and the multiplex bit amount calculation section controls the bit amounts of the moving image encoded signals sent from the accumulation sections to the multiplexing section based on the plurality of second input bit amounts.
In another embodiment of the invention, when the plurality of second input bit amounts calculated by the multiplex bit amount calculation section are different from the corresponding first input bit amounts, the multiplex bit amount calculation section increases the second input bit amounts.
According to still another aspect of the invention, a moving image encoding method for encoding a plurality of moving image signals simultaneously is provided. The method includes encoding all the plurality of moving image signals with the same quantization width.
Alternatively, the moving image encoding method for encoding a plurality of moving image signals simultaneously of this invention includes encoding the plurality of moving image signals with a quantization width obtained based on a difference between a sum of bit amounts of a plurality of moving image encoded signals generated by encoding the plurality of moving image signals and output bit amounts of the plurality of moving image encoded signals output after being temporarily accumulated.
According to still another aspect of the invention, a moving image multiplexing method for multiplexing a plurality of moving image encoded signals after being accumulated in a plurality of accumulation sections is provided. The method includes the steps of: (1) calculating a time period from when a specific bit of each of the plurality of moving image encoded signals is input into a decoding device having an input buffer until when the specific bit is decoded; (2) calculating a bit amount of a frame including the specific bit of each of the plurality of moving image encoded signals accumulated in the plurality of accumulation sections; and (3) determining a plurality of multiplex bit amounts to be multiplexed from the plurality of moving image coded signals based on calculation results from steps (1) and (2).
In one embodiment of the invention, step (3) includes the steps of: (4) determining a plurality of first parameters each of which is a ratio of the bit amount obtained in step (2) to the time obtained in step (1); (5) determining a second parameter which is a sum of the plurality of first parameters; (6) determining a plurality of third parameters each of which is a ratio of each of the plurality of first parameters to the second parameter for the plurality of moving image encoded signals; and (7) determining the plurality of multiplex bit amounts based on the plurality of third parameters.
In still another embodiment of the invention, an input multiplex bit amount used for multiplexing each of the plurality of moving image encoded signals is set at a minimum value among (1) the multiplex bit amount determined based on the third parameter, (2) the bit amount of the moving image encoded signal accumulated in the accumulation section, and (3) an empty capacity of the input buffer of the decoding device, and each of the bit amounts to be multiplexed is controlled using the input multiplex bit amount.
In still another embodiment of the invention, when at least one of the input multiplex bit amounts is different from the corresponding multiplex bit amount, the input multiplex bit amount is increased.
Alternatively, in the moving image multiplexing method for multiplexing a plurality of moving image encoded signals of this invention, a plurality of multiplex bit amounts corresponding to the plurality of moving image encoded signals is preset at zero. The method includes the steps of: (1) calculating a frame bit amount of a frame including a specific bit of each of the plurality of moving image encoded signals; (2) calculating a time period until each of the plurality of moving image encoded signals is decoded; (3) selecting the moving image encoded signal where the time period obtained in step (2) is shorter than a predetermined time value; (4) determining a plurality of primary multiplex bit amounts based on the frame bit amount of the moving image encoded signal selected in step (3); (5) calculating a sum of the plurality of primary multiplex bit amounts; (6) adding the plurality of primary multiplex bit amounts to the plurality of multiplex bit amounts; and (7) renewing the predetermined time value, wherein steps (1) to (7) are repeated, and, if the sum of the plurality of primary multiplex bit amounts is larger than a predetermined bit amount, a plurality of secondary multiplex bit amounts are determined and added to the plurality of multiplex bit amounts, to multiplex the moving image encoded signals of the plurality of multiplex bit amounts.
Thus, since the moving image encoded signals are multiplexed in such a manner that the encoded signal of the frame which will be decoded earlier is multiplexed earlier, the occurrence of overflow or underflow is prevented at the decoding of the moving image encoded signals by the decoding device.
Alternatively, the moving image multiplexing method for multiplexing a plurality of moving image encoded signals of this invention includes the steps of: determining a plurality of minimum transmission amounts required for preventing underflow of a plurality of input buffers of decoding devices based on bit amounts of frames of the plurality of moving image encoded signals which have not been transmitted to the decoding devices and times required until the frames of the plurality of moving image encoded signals are decoded; determining a plurality of transmission bit amount lower limits based on the plurality of minimum transmission amounts; and multiplexing the plurality of transmission bit amount lower limits before multiplexing the plurality of moving image encoded signals.
Alternatively, the moving image encoding device for encoding a plurality of moving image signals of this invention includes: a plurality of encoding sections for encoding the plurality of moving image signals, each of the plurality of encoding sections including a quantization sub-section for quantizing the moving image signals with a predetermined parameter and a stuffing sub-section for stuffing the quantized moving image signals with a predetermined stuffing amount; a quantization control section for controlling the parameters used by the quantization sub-sections simultaneously; a plurality of accumulation sections for temporarily accumulating a plurality of moving image encoded signals output from the plurality of encoding sections; a multiplexing section for multiplexing the plurality of moving image encoded signals accumulated in the plurality of accumulation sections and outputting the multiplexed signals at a constant bit rate; a stuffing control section for controlling the stuffing amounts used by the stuffing sections; and a virtual empty capacity calculation section for calculating an empty capacity of each of a plurality of input buffers of decoding devices after a lapse of a predetermined time period when the plurality of moving image encoded signals are not input into the input buffers for the predetermined time period, wherein the quantization control section determines the parameters used by the quantization sub-sections based on a sum of the bit amounts of the plurality of moving image encoded signals, and the stuffing control section controls each of the stuffing sections based on a sum of the bit amounts of the moving image encoded signals accumulated in the plurality of accumulation sections, the constant bit rate, and a difference between the bit amount of each of the moving image encoded signals accumulated in the accumulation section and the empty capacity of the input buffer obtained by the virtual empty capacity calculation section.
Alternatively, the moving image encoding method of this invention encodes a plurality of moving image signals simultaneously using predetermined quantization widths each based on a difference between a sum of bit amounts of a plurality of moving image encoded signals generated by encoding the plurality of moving image signals and an output bit amount of each of the plurality of moving image encoded signals output after being temporarily accumulated, wherein a plurality of encoded buffer occupations of the moving image encoded signals temporarily accumulated are calculated, an empty capacity of each of a plurality of input buffers of decoding devices after a lapse of a predetermined time period when the moving image encoded signals are not input into the input buffers for the predetermined time period is calculated; and for each of the moving image encoded signals where a buffer differential value obtained by subtracting the empty capacity of the input buffer from the encoded buffer occupation is smaller than a predetermined value, a signal of a bit amount obtained by adding the buffer differential value larger than the predetermined value which does not influence the encoding is distributed to the moving image encoded signals where the buffer differential value is smaller than the predetermined value to effect stuffing.
In one embodiment, the predetermined value is 0.
Alternatively, the moving image encoding device for encoding a plurality of moving image signals of this invention includes: a plurality of encoding sections for encoding the plurality of moving image signals, each of the plurality of encoding sections including a quantization sub-section for quantizing the moving image signals with a predetermined parameter; a quantization control section for controlling the parameters used by the quantization sub-sections simultaneously; a plurality of accumulation sections for temporarily accumulating a plurality of moving image encoded signals output from the plurality of encoding sections; a multiplexing section for multiplexing the plurality of moving image encoded signals accumulated in the plurality of accumulation sections and outputting the multiplexed signals at a constant bit rate; a virtual empty capacity calculation section for calculating an empty capacity of each of a plurality of input buffers of decoding devices after a lapse of a predetermined time period when the plurality of moving image encoded signals are not input into the input buffers for the predetermined time period, wherein the quantization control section determines each of the parameters used by the quantization sub-sections based on a sum of the bit amounts of the moving image encoded signals accumulated in the plurality of accumulation sections, the constant bit rate, and a difference between the bit amount of the moving image encoded signal accumulated in the accumulation section and the empty capacity of the input buffer obtained by the virtual empty capacity calculation section.
Alternatively, the moving image encoding method of this invention encodes a plurality of moving image signals simultaneously using predetermined quantization widths each based on a difference between a sum of bit amounts of a plurality of moving image encoded signals generated by encoding the plurality of moving image signals and an output bit amount of each the plurality of moving image encoded signals output after being temporarily accumulated. The method includes the steps of: calculating a plurality of encoded buffer occupations of the moving image encoded signals temporarily accumulated, calculating an empty capacity of each of a plurality of input buffers of decoding devices after a lapse of a predetermined time period when the moving image encoded signals are not input into the input buffers for the predetermined time period; and encoding each of the moving image encoded signals where a buffer differential value obtained by subtracting the empty capacity of the input buffer from the encoded buffer occupation is smaller than a predetermined value using a quantization width smaller than the corresponding predetermined quantization width.
Thus, even when the generated bit amount of the moving image signal suddenly increases because a corresponding portion of an image is extremely complicated, the occurrence of underflow in the input buffer at the decoding of the moving image encoded signals by the decoding device is prevented.
In one embodiment of the invention, the predetermined value is 0.
Alternatively, the moving image encoding method of this invention encodes a plurality of moving image signals simultaneously using predetermined quantization widths each based on a difference between a sum of bit amounts of a plurality of moving image encoded signals generated by encoding the plurality of moving image signals and an output bit amount of each the plurality of moving image encoded signals output after being temporarily accumulated. The method includes the steps of: calculating a plurality of encoded buffer occupations of the moving image encoded signals temporarily accumulated, calculating an empty capacity of each of a plurality of input buffers of decoding devices after a lapse of a predetermined time period when the moving image encoded signals are not input into the input buffers for the predetermined time period; and encoding each of the moving image encoded signals where a buffer differential value obtained by subtracting the empty capacity of the input buffer from the encoded buffer occupation is larger than a predetermined value using a quantization width larger than the corresponding predetermined quantization width.
In one embodiment of the invention, the predetermined value is 0.
Alternatively, the moving image encoding method of this invention encodes a plurality of moving image signals simultaneously using predetermined quantization widths each based on a difference between a sum of bit amounts of a plurality of moving image encoded signals generated by encoding the plurality of moving image signals and an output bit amount of each the plurality of moving image encoded signals output after being temporarily accumulated, comprising the steps of: calculating a plurality of encoded buffer occupations of the moving image encoded signals temporarily accumulated, calculating an empty capacity of each of a plurality of input buffers of decoding devices after a lapse of a predetermined time period when the moving image encoded signals are not input into the input buffers for the predetermined time period; and calculating a buffer differential value obtained by subtracting the empty capacity of the input buffer from the encoded buffer occupation for each of the moving image encoded signals, and adding a sum of the buffer differential values which are larger than a predetermined value to the sum of the bit amounts.
In one embodiment of the invention, the predetermined value is 0.
According to still another aspect of the invention, the moving image encoding and multiplexing device for encoding a plurality of moving image signals and multiplexing the encoded signals is provided. The device includes: a moving image switch section for switching a destination of a plurality of input moving images; a plurality of encoding sections for encoding the plurality of input moving images output from the moving image switch section; a multiplexing section for multiplexing the encoded signals output from the plurality of encoding sections; and a control section for switching a switching state of the moving image switch section, an encoding mode of the encoding sections, and a multiplexing mode of the multiplexing sections; wherein the control section switches the encoding mode of the encoding sections and the multiplexing mode of the multiplexing sections depending on the switching state of the moving image switch section.
With the above configuration, the plurality of moving image signals with different precisions can be simultaneously encoded, multiplexed, and output. At this time, the combination of the numbers of input moving image signals for respective levels of precision is not restricted. The simultaneous encoding and multiplexing is also applicable to the cases where all the input moving image signals are independent from one another or all the input moving image signals are generated by screen division. Also, even when the output bit rate after the multiplexing is constant, it is possible to simultaneously encode, multiplex, and output the plurality of individual moving image signals and the plurality of moving image signals generated from one moving image signal by screen division.
In one embodiment of the invention, the control section comprises: a switch control sub-section for switching the switching state of the moving image switch section; an encoding control sub-section for switching the encoding mode of the encoding section; and a multiplexing control sub-section for switching the multiplexing mode of the multiplexing section, and the encoding control sub-section switches the encoding mode depending on the switching state of the moving image switch section, and the multiplexing control sub-section switches the multiplexing mode depending on the switching state of the moving image switch section.
In still another embodiment of the invention, the moving image encoding and multiplexing device further includes a screen division section upstream of the moving image switch section.
In still another embodiment of the invention, the moving image encoding and multiplexing device further includes a moving image time-division section upstream of the moving image switch section.
In still another embodiment of the invention, the moving image encoding and multiplexing device further includes accumulation sections for temporarily accumulating moving image encoded signals output from the encoding sections, wherein the encoding control sub-section determines a parameter for controlling each of the encoding sections based on a sum of bit amounts of the moving image encoded signals accumulated in the accumulation sections.
In still another embodiment of the invention, the multiplexing section comprises: a moving image multiplexing sub-section for multiplexing the plurality of moving image encoded signals and outputting a moving image encoded signal; a channel multiplexing sub-section for multiplexing a plurality of input signals input into the multiplexing section and the output signal output from the moving image multiplexing sub-section; and a switch sub-section for switching the destination of the moving image encoded signals input into the multiplexing section between the moving image multiplexing sub-section and the channel multiplexing sub-section.
According to still another aspect of the invention, an image transmission device is provided. The device includes a plurality of image encoding sections and a transmission processing section, wherein the transmission processing section multiplexes encoded data specified by the image encoding sections every multiplexing timing, transmits the encoded data to a predetermined route, and sends to the image encoding sections multiplexing information which is calculated based on encoded data amount in the image encoding sections and can be used for calculation of a delay amount taken until the encoded data is transmitted to a decoding device, and the plurality of image encoding sections determine quantization widths used at quantization in an image encoding processing based on the multiplexing information sent from the transmission processing section, encode the images, and transmit the encoded data to the transmission processing section every multiplexing timing to specify the encoded data.
In one embodiment of the invention, the transmission processing section comprises a transmission buffer, and the transmission processing section takes the encoded data specified by the image encoding sections in the transmission buffer every multiplexing timing, and outputs the encoded data at a predetermined transmission rate in the order of the taking-in of the encoded data, as well as outputting an occupation of the encoded data in the transmission buffer as multiplexing information.
In one embodiment of the invention, each of the image encoding sections includes: a quantization width determination sub-section; and a basic encoding processing sub-section for encoding images by quantizing the images with a quantization width specified by the quantization width determination sub-section, and the quantization width determination sub-section calculates a buffer occupation in each of a plurality of decoding devices which receive the encoded data transmitted from each of the image encoding sections via the transmission processing section based on the multiplexing information, and sets the quantization width based on the calculated buffer occupation in the decoding device and an amount of encoded data which has not been transmitted.
In another embodiment of the invention, each of the image encoding sections further includes an encoded data memory sub-section for temporarily storing the encoded data, and the encoded data memory sub-section temporarily stores non-transmitted data which has not been transmitted to the transmission processing section among the encoded data every transmission timing, and transmits the encoded data to the transmission processing section using as an upper limit a value preset by each of the image encoding sections or a value obtained by subtracting the buffer occupation in the decoding device calculated based on the multiplexing information from a buffer size of the decoding device predicted by the receiver side.
Alternatively, the image transmission device of this invention includes a transmission processing section for receiving encoded data from a plurality of image encoding sections, wherein the transmission processing section comprises a transmission buffer, takes the encoded data specified by the image encoding sections in the transmission buffer every multiplexing timing, and outputs the encoded data at a predetermined transmission rate in the order of the taking-in of the encoded data, as well as outputting an occupation of the encoded data in the transmission buffer as multiplexing information.
Alternatively, the image encoding device of this invention includes a quantization width determination section and a basic encoding processing section for encoding images by quantizing the images with a quantization width specified by the quantization width determination section, wherein the quantization width determination section determines the quantization width based on multiplexing information which can be used for calculation of a delay amount taken until encoded data is transmitted to a virtual decoding device, a buffer occupation in the virtual decoding device calculated based on the multiplexing information, and an amount of encoded data which has not been transmitted.
In one embodiment of the invention, the image encoding device further includes an encoded data memory section for temporarily storing the encoded data, wherein the encoded data memory section temporarily stores non-transmitted data which has not been transmitted among the encoded data every transmission timing, and outputs the encoded data using as an upper limit a value preset by each of the image encoding sections or a value obtained by subtracting the buffer occupation in the virtual decoding device calculated based on the multiplexing information from a buffer size of the decoding device predicted by the receiver side.
Alternatively, the image transmission device of this invention includes a bit rate management section for managing a bit rate at a transmission route and one or more image encoding sections; wherein the bit rate management section determines a bit rate representing a total of transmission rates at the one or more image encoding sections on the transmission route, allows for transmission of encoded data requested to be transmitted by any of the image encoding sections every transmission timing, and sends transmission information regarding a transmission delay which varies with the allowance to another image encoding section on the transmission route, and the one or more image encoding sections encode images by quantizing the images with a quantization width determined based on the transmission information, non-transmitted encoded data, and a predicted buffer size on the receiver side.
With the above configuration, the image quality of the image signals transmitted on a network can be made substantially uniform.
Alternatively, the image transmission device of this invention includes a bit rate management section for managing transmission rates of a plurality of image encoding sections, wherein the bit rate management section determines a bit rate representing a total of transmission rates at all the image encoding sections on a transmission route, allows for transmission of encoded data requested to be transmitted by any of the image encoding sections every transmission timing, and sends transmission information regarding a transmission delay which varies with the allowance to another one of the image encoding sections on the transmission route.
Alternatively, the image encoding device of this invention sets a quantization width used for quantization based on transmission information regarding a transmission delay which varies with an allowable transmission amount, non-transmitted encoded data, and a predicted buffer size on the receiver side.
Alternatively, the image encoding method of this invention includes the steps of: (1) determining a quantization width; and (2) encoding images by quantizing the images with the quantization width specified in step (1), wherein in step (1) the quantization width is set based on multiplexing information which can be used to calculate a delay amount taken until encoded data is transmitted to a virtual decoding device, a buffer occupation in the virtual decoding device calculated based on the multiplexing information, and an amount of encoded data which has not been transmitted.
In one embodiment of the invention, non-transmitted data which has not been transmitted among the encoded data is temporarily stored every transmission timing, and the encoded data is output using as an upper limit a value preset by each of the image encoding sections or a value obtained by subtracting the buffer occupation in the decoding device calculated based on the multiplexing information from the buffer size of the decoding device predicted by the receiver side.
Alternatively, the image encoding method of this invention includes encoding images by setting a quantization width used for quantization based on transmission information regarding a transmission delay which varies with an allowable transmission amount, non-transmitted encoded data, and a predicted buffer size on the receiver side.
Thus, the invention described herein makes possible the advantages of: (1) providing moving image encoding device/method which output moving images with a uniform quality and prevent the image quality from largely lowering even immediately after a scene change at which the images suddenly become complicated; (2) providing moving image multiplexing device/method which multiplex moving image signals and output the results so that each input buffer of a decoding device does not overflow or underflow; (3) providing moving image encoding and multiplexing device/method which encode moving image signals with different resolutions simultaneously, multiplex the encoded signals, and output the results; and (4) providing an image transmission device in which the quality of images encoded by encoding sections is kept uniform even at a scene change, and, in an application of having encoders dispersed in a network, bit rates are allocated for the encoders depending on the images input therein within the range of an allowable entire bit rate and a uniform image quality is obtained.